1. Field of the Invention
The present invention relates to a roller stocker and a method for fabricating a liquid crystal display (LCD) device and, more particularly, to a roll stocker corresponding to various models of mother substrates and to keeping a sufficient number of rubbing rolls for securing a margin for roll operation, and a fabrication method of a liquid crystal display (LCD) device using the same.
2. Description of the Related Art
As the consumer's interest in information displays is growing and as the demand for portable (mobile) information devices increases, research and commercialization of light and thin flat panel displays (“FPD”) has increased. Flat panel displays may replace the Cathode Ray Tube (“CRT”), which is a common existing display device.
The liquid crystal display (“LCD”) device is a FPD device for displaying images using optical anisotropy of liquid crystal. LCD devices exhibit excellent resolution and color and picture quality, so it is widely applied for notebook computers or desktop monitors, and the like.
In the LCD device, a data signal according to image information is separately supplied to liquid crystal cells arranged in a matrix form and light transmittance of the liquid crystal cells is controlled for displaying the desired image.
FIG. 1 is an exploded perspective view illustrating the structure of a LCD device.
As illustrated in FIG. 1, the LCD device includes a color filter substrate 5, namely, a first substrate, an array substrate 10, namely, a second substrate, and a liquid crystal layer 40 formed between the color filter substrate 5 and the array substrate 10.
The color filter substrate 5 includes a color filter (C) comprising sub-color filters 7 for implementing red (R), green (G) and blue (B) color, a black matrix 6 for discriminating the sub-color filters 7 and blocking light transmitting through the liquid crystal layer 40, and a transparent common electrode 8 for applying a voltage to the liquid crystal layer 40.
The array substrate 10 includes gate lines 16 and data lines 17 that are arranged on the substrate 10 and define pixel regions (P). A thin film transistor (TFT) switching element is formed at respective crossings of the gate lines 16 and the data lines 17, and a pixel electrode 18 is formed at each pixel region (P).
The pixel region (P) is a sub-pixel corresponding to one sub-color filter 7 of the color filter substrate 5, and a color image is obtained by combining the red, green and blue types of sub-color filters 7. Namely, the three red, green and blue sub-pixels form one pixel, and TFTs are connected to the blue, green and blue sub-pixels.
An alignment film (not illustrated) for aligning liquid crystal molecules of the liquid crystal layer 40 is formed on the color filter substrate 5 and the array substrate 10.
FIG. 2 illustrates a method for forming an alignment film using a roll printing method.
As illustrated, generally, an alignment film is formed using a printing method using a plurality of rolls. Namely, an alignment solution 24 supplied between a cylindrical anylox roll 22 and a cylindrical doctor roll 23 is uniformly coated entirely on the anylox roll 22 as the anylox roll 22 and the doctor roll 23 are rotated. In this case, the alignment solution 24 is supplied by a dispenser 1 in an injector type.
The anylox roll 22 is rotated in contact with a printing roll 24 having a rubber plate 25 attached on a certain region of its surface, thereby transferring the alignment solution 29 on the anylox roll 22 to the rubber plate 25. The rubber plate 25 corresponds to a substrate 26 on which the alignment solution 29 is to be coated, and has a master pattern to allow the alignment film to be selectively printed on the substrate 26.
As a printing table 27 with the substrate 26 loaded thereon is moved in contact with the printing roll 24, the alignment solution 29 which has been transferred to the rubber plate 25 is re-transferred onto the substrate 26 to thereby form an alignment film.
Next, with the alignment film formed on the substrate, the alignment film is rubbed to arrange liquid crystals in a certain direction to form valleys in a certain direction.
FIG. 3 is a perspective view illustrating a rubbing process.
As illustrated, the alignment film 21 is rubbed to form recesses 36 on the surface thereof. The rubbing process rubs the surface of the alignment film 21 in a certain direction using a roller 30 with a rubbing cloth 35 wound thereon.
After the surface of the alignment film 21 is rubbed, it has fine recesses 36.
For the rubbing cloth 35, a soft cloth is used. The rubbing equipment, including the roller 30, is relatively simple. The basic part for setting conditions for the rubbing process is setting a rubbing condition with a suitable strength and applying a uniform rubbing strength on a large area.
If the rubbing is not uniformly performed, an alignment degree of liquid crystal molecules is not spatially uniform, causing a defect that optical characteristics are different at a certain portion.
In addition, since the physical units such as the rolls are used in the rubbing process, management of the rolls is important with respect to stability of processes. Accordingly, it is important to secure a sufficient number of rubbing rolls to obtain a margin in operating rolls. However, there is no means for keeping the rubbing rolls, and the rubbing rolls are kept standing vertically, limiting the operation of rolls. In addition, as the size of the mother substrate for fabricating a liquid crystal display panel increases, the corresponding rubbing roll lengthens, so there is a limitation on keeping rubbing rolls in a standing state in a limited clean room.